Won't crank. Tried to jump with screwdriver across terminals at starter but nothing... Already replaced it and it ran fine for a couple of days then it just wouldn't start again and same thing won't crank can't jump at starter and when hooked up to the battery charger battery is showing to be ready to go.

 

How old is the battery on your Chevy?

 

Check your battery cables for corrosion and tight connections. Do this at both ends as you might have a problem with the ground cable connection to the engine block.

 

If the Cold Cranking Amps (CCA) are low, you'll need a new battery. Simply having 12.5 volts won't cut it in the winter-time. The jokers at the major auto parts stores seem to be unaware of this fact, After all they need to sell things, but in this case it might well be your battery gone south. Same thing with A/C systems come hot weather, and the A/C system won't operate properly.

 

It is obviously a bad connection.

The battery has a full 12.5V charge, but the starter motor won't start! It won't even make a sound!

Plus, you just did some work on it, so there's a 50% chance that your poor work caused the recent issue.

First, start with the battery.

You said you've got a full 12.5V charge. Good!

Second, re-check the terminals on the battery. Gotta make sure they're CLEAN and SNUG.

Thirdly, re-check the cable connection from the battery to the starter. Again, gotta be clean and snug, AND WHILE YOU'RE DOWN THERE, persuade it with a couple taps from a hammer or a wrench, just to jiggle the mechanism a bit. It could work (but if it does, you'll wanna replace that starter, bcuz it's bad; but in this case, not likely, since it's new).

Fourthly, recheck the cable connection from the battery to the alternator.

Lastly, re-check the connection from the negative terminal of the battery (black) to the chasis ground. Again, must be clean and snug.

Just re-check all the major connections and make sure you've got at least 12.5V, and rap the starter a couple of times for good measure.

It's either poor work by you or a bad starter.

Or a disconnected electrical connector somewhere.